A tracked machine, such as a track-type tractor or excavator, is typically supported and propelled by a pair of drive track undercarriages. Each of drive track undercarriage includes an endless chain having a plurality of interconnected articulating components or links. Each drive track undercarriage typically also includes a drive wheel or sprocket and one or more idlers. The chain is advanced around the sprocket and the one or more idlers.
During operation of the work machine, it is necessary to maintain tension on the chain in order to keep the chain from derailing or from jumping between teeth on the sprocket. In order to maintain tension on the chain, a tension adjustment mechanism such as a hydraulic cylinder or coiled spring is often included in the drive track undercarriage.
With regard to excavators and other similar track machines, it is generally desirable to have the chain relatively taut during performance of a digging or other type of work operation in order to prevent the excavator from rolling back and forth within the interior of the chain as a result of recoil forces generated during performance of the work operation. When digging with a tight chain, the machine feels more stable to the operator and less wear occurs to the track components. To create tension on the chain, the hydraulic or grease-filled cylinder of the tension adjustment mechanism urges the idler away from the drive wheel.
In contrast, it is generally desirable to have the chain relatively loose during advancement or travel of an excavator or other similar track machines. By loosening or otherwise decreasing tension on the chain below the tension used when digging, wear on the components associated with the drive track undercarriage is reduced. This increases the efficiency and useful life of the excavator. To reduce tension in the chain, the hydraulic or grease-filled cylinder of the tension adjustment mechanism allows the idler to move toward the drive wheel.
The tension adjustment mechanism may also provide a recoil function in the chain, which accommodates temporary forces on the track such as when a rock or the like becomes wedged between the track and the wheels. In these instances, the idler is permitted to recoil toward the drive wheel in order to accommodate the extra length the track must encircle in order to accommodate the rock without breaking. The recoil function may be performed by a gas filled shock absorbing telescoping section. In contrast, the tension adjustment function may be performed by a hydraulic or grease-filled telescoping section.
A problem arises when one of these two sections develops a leak. Because the entire recoil and tension adjustment assembly is contained within the housing, the operator has difficulty in identifying which section is leaking and therefore which section requires maintenance.